As Aquamorph Entity enters the battlefield or is turned face up, it becomes your choice of 5/1 or 1/5.
Morph 2U (You may cast this face down as a 2/2 creature for 3. Turn it face up any time for its morph cost.)

If four or more creatures are attacking, you may pay 1W rather than pay Arrow Volley Trap's mana cost.
Arrow Volley Trap deals 5 damage divided as you choose among any number of target attacking creatures.